A possible plot is that Voldemort discovers the existence of the demigods and tries to use their powers for his own evil purposes. He sends his Death Eaters to capture some demigods. Percy and his friends manage to escape and seek refuge at Hogwarts. At Hogwarts, they learn about magic in a whole new way while also teaching the wizards and witches about their own powers. The two groups then have to combine their skills, like the demigods' combat abilities and the wizards' spell - casting, to fight against Voldemort and his new - found allies from the world of Greek mythology.
The characters' interactions are also fascinating. Imagine Harry Potter meeting Percy Jackson. They come from different but equally dangerous worlds. Harry could be intrigued by Percy's ability to control water, and Percy might be curious about Hogwarts. Fanfictions often play with these crossovers to create unique friendships or rivalries.
One popular pairing is Harry Potter and Percy Jackson themselves. Their different personalities and powers make for an interesting dynamic. They could be seen as allies, learning from each other's strengths and weaknesses.
One interesting plot could be that the magical worlds of Hogwarts and Camp Half - Blood somehow merge. Harry Potter and his friends find themselves in the world of Percy Jackson, facing off against mythological creatures they've never seen before. Maybe they have to work together to stop a common enemy that threatens both their worlds, like an ancient dark magic that is starting to corrupt the gods and the wizards alike.
One great example could be a story where Percy and his friends from Camp Half - Blood end up at Hogwarts. Maybe they are there to help fight a new dark force that threatens both the wizarding world and the demigod world. In this crossover, Percy could use his water - controlling abilities in the Hogwarts lake, and Harry could show Percy some cool magic spells.
Friendship and loyalty are also big themes. Since it's a crossover, the characters from both series have to learn to trust and work together. The harem aspect adds another layer to this, as the relationships between the characters are more complex. For example, they might have to protect each other not just as friends but also as part of the harem - like group.
The settings are different. Harry Potter is set mainly in the UK, at Hogwarts School of Witchcraft and Wizardry and other wizarding locations. Percy Jackson is set in modern - day USA, with a lot of action taking place at Camp Half - Blood. Also, the magic systems vary. In Harry Potter, there are spells, potions, and magic wands. In Percy Jackson, the demigods have powers related to their godly parentage like Percy can control water because his father is Poseidon. So they are clearly not related in a fanfiction way.
The idea of facing a common enemy is also very prevalent. It could be a new threat that neither world alone could handle. This brings the characters together and forces them to combine their unique skills and knowledge. For example, a dark force that has elements of both Greek mythology and dark wizardry. There's also the theme of discovery. Characters from one world getting to discover the new and strange elements of the other world, like a demigod experiencing the joys of butterbeer or a Hogwarts student seeing a centaur for the first time.
Percy would probably be really curious about the wizarding world. He might ask Harry a million questions about how magic works. Harry, on the other hand, would be intrigued by Percy's ability to control water and his connection to the gods. Hermione would likely be very interested in learning about Greek mythology from Percy and his friends, and she might try to find books in the Hogwarts library about it. Ron might be a bit more hesitant at first, but once he sees Percy's sword - fighting skills, he'd be impressed.
One idea could be that the demigods and wizards have to team up to fight a common enemy that is threatening both the magical and the mythological worlds. For example, a dark force that can manipulate both magic and the powers of the gods. Another plot could involve Percy and his friends getting lost in the wizarding world and having to navigate Hogwarts while also dealing with their own demigod issues. Maybe they discover that some of the magic in the wizarding world has its roots in the ancient Greek magic that the demigods are familiar with.